This invention is suitable for a fuel injection valve, particularly a fuel injection valve for cylinder injection, and relates to a structure of the fuel injection valve for injecting fuel from a fuel injection hole be applying swirl energy to a fuel flow.
FIG. 8 is a sectional side view showing the entire configuration of a conventional fuel injection valve 71 for cylinder injection. The fuel injection valve 71 for cylinder injection comprises a housing body 72 and a valve unit 73 which is swaged in one end of this housing body 72 and is covered with a holder 105. A fuel supply pipe 74 is connected to the other end of the housing body 72 and high-pressure fuel is supplied from this fuel supply pipe 74 into the fuel injection valve 71 for cylinder injection through a fuel filter 127. Also, the top end of the fuel injection valve 71 for cylinder injection is inserted into an insertion hole 76 for injection valve of a cylinder head 75 of an internal combustion engine and is sealed and mounted by a wave washer 130.
The valve unit 73 comprises a stepped hollow cylindrical-shaped valve body 79 having a small diameter cylindrical part 77 and a large diameter cylindrical part 78, a valve seat 81 which is fixed in the top of a center hole within the valve body 79 and has a fuel injection hole 80, a needle valve 82 which is a valve element for opening or closing the fuel injection hole 80 by making or breaking contact with the valve seat 81 using a solenoid unit 120 (described later), and a swirl body 83 which guides the needle valve 82 in the axial direction and applies swirl movements to fuel flowing into the fuel injection hole 80 of the valve seat 81 inwardly in the diameter direction. The valve body 79 of the valve unit 73 forms a housing of the fuel injection valve 71 for cylinder injection in cooperation with the housing body 72.
The housing body 72 comprises a first housing 100 having a flange 100a for mounting the fuel injection valve 71 for cylinder injection in the cylinder head 75, and has the solenoid unit 120 within the first housing 100. The solenoid unit 120 comprises a bobbin 122 wound by a coil 121 and a core 123 installed in an inner circumferential portion of this bobbin 122, and a winding of the coil 121 is connected to a connection terminal 126. The core 123 is formed in a hollow cylindrical shape so that the inside of the core 123 is used as a fuel passage, and a spring 125 is suspended between a sleeve 124 and the needle valve 82 in the hollow portion of the core 123.
A moving armature 101 is mounted in the other portion of the needle valve 82 in opposition to the top side of the core 123, and also the intermediate portion of the needle valve 82 is provided with a guide 82a for sliding and guiding the needle valve 82 along an inner circumferential surface of the valve body 79 and a needle flange 82b in engagement with a spacer 102 installed in the first housing 100.
FIG. 9 is an enlarged sectional side view showing the vicinity of the valve seat of the valve unit 73 and FIG. 10 is a front view seen from the side of the valve seat 81 of the swirl body 83. In the drawings, the swirl body 83 of the valve unit 73 is a member with a substantially hollow cylindrical shape having a center hole 85 for surrounding the needle valve 82 (valve element) in the center and slidably supporting it in the axial direction, and comprises a first end surface 86 in engagement with the valve seat 81, a second end surface 87 opposite to the valve seat 81, and a circumferential surface 89 having a portion in engagement with an inner circumferential surface 88 of the valve body 79 being a part of a hollow housing between these end surfaces when the swirl body 83 is assembled in the valve unit 73.
The second end surface 87 of the swirl body 83 is supported in engagement with a shoulder part 90 of the inner circumferential surface 88 of the valvehody 79 in the periphery, and also it is configured so that a passage groove 91 extending in the diameter direction is formed and fuel can flow from the inner circumferential portion to the outer circumferential portion of the second end surface 87.
The circumferential surface 89 of the swirl body 83 is provided with a plurality of outer circumferential surface parts 89a for defining a position to the valve body 79 in engagement with the inner circumferential surface 88 of the valve body 79 and a flow passage part 89b which is disposed between these outer circumferential surface parts 89a and forms an axial flow passage 92 of fuel along with the inner circumferential surface 88.
The axial end surface facing the valve seat 81 of the swirl body 83, namely the first end surface 86 is provided with an inner circumferential ring groove 94 with a predetermined width formed on an inner circumferential side adjacent to the center hole 85 of the first end surface 86, and a swirl groove 95 which is connected to the flow passage part 89b of the circumferential surface 89 at one end and extends inwardly in the approximately diameter direction therefrom and is connected to the inner circumferential ring groove 94 in the tangential direction at the other end.
Next, an operation of the fuel injection valve for cylinder injection will be described. Referring first to FIG. 8, when energizing the coil 121 of the solenoid unit 120 through connection terminal 126 from the outside, a magnetic flux is generated in a magnetic passage formed by the moving armature 101, the core 123 and the housing body 72, and the moving armature 101 is attracted to the side of the core 123 against an elastic force of the spring 125. Then, the needle valve 82 integral with the moving armature 101 moves to the right side (shown in FIG. 8) of a predetermined stroke until the needle flange 82b is brought into engagement with the spacer 102. Incidentally, the needle valve 82 is guided and held in the inner circumferential surface of the valve body 79 by the guide 82a. 
Then, in FIGS. 9 and 10, when the top end of the needle valve 82 moves away from the valve sear 81 to form a gap, highxe2x80x94pressure fuel of introduced from the fuel supply pipe 74 first flows into the axial flow passage 92 of the circumferential surface from a passage between the valve body 79 and the needle valve 82 through the passage groove 91 of the second end surface 87 of the swirl body 83. Next, the high-pressure fuel flows into the swirl groove 95 of the first end surface 86 of the swirl body 83 inwardly in the diameter direction and flows into the inner circumferential ring groove 94 of the first end surface 86 in the tangential direction and forms swirl flow in a swirl chamber W constituted by the inner circumferential ring groove 94. Subsequently, the fuel flows into the injection hole 80 of the valve seat 81 and is sprayed from an outlet of the top of the injection hole 80.
Since the conventional fuel injection valve is configured as described above, a non-contact portion remains between the outer circumferential surface of the swirl body and the inner circumferential surface of the valve element, with the result that there was a problem that another radiator is required in case where combustion heat is large and temperature in the top of the fuel injection valve tends to become high. Also, in case of a specification of the swirl groove with a large sectional area, there was a problem that the axial flow passage relatively becomes narrow, so that pressure loss occurs in the axial flow passage and a desired flow velocity cannot be obtained in the swirl groove.
The invention is implemented to solve such problems, and it is an object of the invention to provide a fuel injection valve capable of achieving weight reduction of a swirl body while speeding heat radiation from the swirl body.
A fuel injection valve according to first aspect of the invention comprises a hollow-shaped valve body, a valve seat which is provided in the one end of this valve body and has a fuel injection hole, a valve element which moves within the valve body and makes or breaks contact with the valve seat to open or close the fuel injection hole, and a swirl body which is arranged around the valve element and slidably supports the valve element and also applies swirl to fuel flowing from the fuel injection hole, and further most of an outer circumferential part of the swirl body is in a full circumference engagement with an inner circumferential surface of the valve body.
In the fuel injection valve according to second aspect of the invention, the upstream portion of swing grooves provided in the swing body is formed in a common passage.
In the fuel injection valve according to third aspect of the invention, the common passage is constructed by a doughnut-shaped common passage.
In the fuel injection valve according to forth aspect of the invention, ribs are respectively formed between an inner surface of the outer circumferential part of the swirl body and a bottom part of the doughnut-shaped common passage and between an outer surface of a support part of the valve element and the bottom part of the doughnut-shaped common passage.
In the fuel injection valve according to fifth aspect of the invention, one end surface of the swirl body is in engagement with the valve seat while the other end surface is in engagement with a shoulder part of the valve body.
In the fuel injection valve according to sixth aspect of the invention, the swirl grooves provided in the swirl body are eccentric to a valve stem a: a constant distance and the side distant from this valve stem of the swirl grooves is connected to an outer circumference of a ring groove in the tangential direction.
In the fuel injection valve according to seventh aspect of the invention, a clearance fit is made so that a diametral clearance between an outer circumferential surface portion of the swirl body and an inner circumferential surface portion of the valve body is 7 xcexcm or less.
In the fuel injection valve according to eighth aspect of the invention, the outer circumferential surface portion of the swirl body and the inner circumferential surface portion of the valve body are assembled by a press fit.